Interpretive Summary: Blueberries are grown in more than 30 states on over 16,400 hectares in the USA. The blueberry industry in Georgia continues to grow rapidly, with substantial acreage increases on a yearly basis. Due to the age of the industry in Georgia, many plantings are now reaching >20 year timeframe, and producers are often deciding to replant these older sites, as opposed to purchasing new land. As a result, replant disorder, a general poor growth and decline associated with plant-parasitic nematodes, is a occurring. Several plant-parasitic nematode species, including stubby root, spiral, dagger, and ring nematodes, have been reported to be associated with commercially grown blueberries in the USA. Determining the effect of ring nematode on the growth and yield of blueberry plants is warranted.
In August 2009, the pathogenicity of ring nematode on Rabbiteye blueberry was tested under greenhouse and field microplot conditions in GA. Results indicate that the nematode populations increased in all the treatments, but the rate of their reproduction was greatest in the treatments receiving the lowest initial population level (10 nematodes per plant) 75 and 150 days after inoculation at both locations. We also observed poor plant growth in nematode treated pots as compared to the untreated pots, suggesting that the ring nematode, M. ornata, is a likely pathogen to blueberry plants.
These data provide useful insights into the host-parasitic relationships between ring nematode and blueberry replant disorder and the need for developing appropriate nematode management strategies in blueberries grown in the Southeast.

Technical Abstract:
Blueberries, Vaccinium spp., are grown in more than 30 states on over 16,400 hectares in the United States. The blueberry industry in Georgia continues to grow rapidly, with substantial acreage increases on a yearly basis. Several plant-parasitic nematode species, including stubby root (Paratricodorus sp.), spiral (Helicotylenchus sp.), dagger (Xiphinema sp) and ring Mesocriconema ornata nematodes, have been reported to be associated with three types of commercially grown blueberries in the United States. However, there is no data available on the effects of plant-parasitic nematodes on the growth and yield of blueberry plants. Therefore, we initiated an experiment in August 2009 to test the pathogenicity of M. ornata on Rabbiteye blueberry (Vaccinium ashei Reade) variety “Alapaha” under greenhouse conditions in Athens, GA, and under field microplot conditions in Byron, GA. Single one-year-old blueberry plants were transplanted into plastic pots (surface area 346 cm2) containing 10 kg autoclaved sandy loam soil (pH ~ 5.0). Eight weeks after transplanting, plants were inoculated with five different nematode inoculum levels (treatments) including 0 (water control), 10, 100, 1000 and 10,000 mixed stages of ring nematodes per plant. The nematode population in each pot was assessed 75 and 150 days after inoculation by randomly removing four soil cores (2.5 cm diam. x 10 cm deep) from the root area around each plant. Individual soil cores were combined into a composite sample, and nematodes were extracted from 100-g soil sub-samples. Nematode population densities were expressed as numbers of nematodes/pot, and their reproduction rates (Pf/Pi) were then calculated by dividing the total number of nematodes per pot (Pf = final population) by the number of nematodes added (Pi = initial population). We found that the nematode populations increased in all the treatments, but the rate of their reproduction was greatest in the treatments receiving the lowest initial population level (10 nematodes per plant) 75 and 150 days after inoculation at both locations. We also observed poor plant growth in nematode treated pots as compared to the untreated pots, suggesting that the ring nematode, M. ornata, is a likely pathogen to blueberry plants. Thus, these preliminary findings demonstrate for the first time that ring nematode, M. ornata, is a potential pest of blueberry in Georgia.